This invention relates to pressure regulators.
Conventional diaphragm pressure regulators regulate gas pressures with acceptable accuracy, but require a large number of components. For example, in the typical diaphragm regulator shown in the Gas Regulator Handbook, published by Rockwell Manufacturing Company, Pittsburgh, Pa., 1959, p. 26, a separate adjusting screw is needed to compress the main spring, several parts are needed to couple the spring to the diaphragm, and the valve assembly below the diaphragm comprises several parts. It is desirable to minimize the number of parts in order to reduce the number of assembly operations to facilitate automation of the manufacture of the regulators with consequent reduction of manufacturing cost.
Piston pressure regulators require many fewer parts than do diaphragm regulators. For example, by screwing the cap onto the base, the main spring is compressed without the need for a separate adjusting screw, and a piston and seal replace the diaphragm assembly. However, the friction force of the seal subtracts directly from the main spring force, thereby changing the outlet pressure. This friction is erratic, since piston regulators use O-ring seals which have a stick-slip characteristic, and can cause oscillations in use. Hence errors are generally greater than with the diaphragm regulator. Piston regulators also tend to be longer than diaphragm regulators, because three elements are assembled in line: the base, the piston, and the spring. The piston length/diameter ratio must be at least 1:1 to prevent jamming. A diaphragm, on the other hand, takes up almost no space lengthwise in the regulator. It is desirable to make a pressure regulator as compact as possible--lengthwise and widthwise.
One prior art piston device currently available on the market is the Fuel Gas Pre-Set Regulator No. 8060032 (CGA-510) manufactured by Air Reduction Co., Inc. of New York, N.Y. It uses an O-ring seal which is not annular with the spring but located below it. A piston device using an O-ring which is annular with the spring is described in Mays U.S. Pat. No. 3,791,412.